GCS_Mavlink: New message def: MAV_CMD_NAV_CONTINUE_AND_CHANGE_ALT
GCS_MAVLink: include units in CONTINUE_AND_CHANGE_ALT
GCS_MAVLink: code generation from XML for MAV_CMD_CONTINUE_AND_CHANGE_ALT.
AP_Mission: support for MAV_CMD_CONTINUE_AND_CHANGE_ALT
Plane: Implementation of MAV_CMD_CONTINUE_AND_CHANGE_ALT.
Plane: Keep throwing WP in front plane for CONTINUE_AND_CHANGE_ALT
Plane: fixed CONTINUE_AND_CHANGE_ALT command

current_loc should be used, not prev_WP_loc
AP_Mission: Support MAV_CMD_DO_FENCE_ENABLE as a mission item.
Plane: Support MAV_CMD_DO_FENCE_ENABLE as a mission item.
Plane: fixed missing break statement
AP_Math: fixed example build
Plane: prepare for 3.2.0 release